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4 Vertebral body cage use in thoracolumbar fractures: Outcomes in a prospective series of 23 cases at 2 years follow-up 605 Figure 5 Subsequently, no evolution in kyphosis was observed. CT found fusion at 6 months in all cases (Fig. 5). Discussion Anatomically, ideal vertebral body fracture management would provide complete and enduring correction of vertebral kyphosis. Some authors reported no correlation between radiologic correction of vertebral kyphosis and clinical outcome [8,9]; others found a strong correlation between residual kyphosis and poor functional results [10,11]. We consider vertebral body replacement to be indicated in major vertebral fracture threatening spinal stability and statics. The objective is to avoid evolutive kyphosis. We therefore indicate surgery in case of any of the following five criteria: > 50% reduction in vertebral height, RTA>20, > 50% canal narrowing, major discoligamentary lesion, or neurologic deficit [2]. McCormack, in 1994, quantified vertebral body destruction on the score named for him [12]. He determined the Arthrodesis fusion at 6 months. risk of posterior osteosynthesis material rupture or insufficiency, recommending anterior vertebral body replacement accordingly. He pointed out, however, that his score failed to confirm ligamentary involvement, and could therefore not provide formal indication. Having performed primary posterior osteosynthesis in only half of the present cases, we did not use the McCormack score. Vertebral body replacement can be 1- or 2-step. Onestep surgery associates lateral osteosynthesis to vertebral body replacement in a single procedure [13,14], while 2-step surgery performs primary lateral osteosynthesis followed 5 or 6 days later by anterior replacement if step-1 control CT confirms the indications for step 2: > 50% residual vertebral height loss, RTA > 20, and > 50% canal narrowing (Fig. 6) [15]. Posterior instrumentation can then be minimized and arthrodeses restricted to two mobile segments [16]. We argue for the 2-step attitude, as primary posterior osteosynthesis reinforces assembly stability, and enables primary RTA correction, facilitating the installation of the cage. It is especially to be recommended in primary surgery Figure 6 Two-step primary surgery. Primary posterior osteosynthesis allows initial RTA correction, facilitating cage positioning.

5 606 N. Salas et al. Table 2 Comparison between the present and recent series. Ulmar et al. [27] Knop et al. [28] Payer [29] Lange et al. [30] Present series Patients FU (mo) Surgery time (min) 144(75 275) 183 ( ) 180 ( ) 302 ( ) a 270 ( ) b Blood-loss (ml) 640 (500 1,200) ( ) a 1422 ( ) b Hospital stay (days) (7 45) a 15 (7 30) b VAS at 1 yr 1.5/ /10 Postop RTA 13.8 Correction 18.6 ± 10 RTK: 2 Correction ± 6 (+6 to 11 ) Correction loss ± ± ± 2.5 Consolidation 4 late 100% 4 late1 non-union 100% 1 non-union a All 23 patients of the series. b Minimally invasive approach only. as emergency or late-emergency (1 5 days) corpectomy involves significant bleeding which usually requires transfusion [14,17]. Using a cage avoids the risk of secondary resorption incurred when a structural bone graft is used alone, and thus of correction loss or non-union [18]. Being expandable and modular, it adapts to the corpectomy space. It also avoids such graft-related risks as severe pain, hematoma and infection. Minimally invasive approaches [19 25] reduce morbidity by reducing surgery time, bleeding and hospital stay and also minimizing anatomic structure lesions and functional sequelae and blemishes. However, this attitude still requires familiarity with the classical approaches in case of crossover, with help available from a vascular or thoracic surgeon. The peroperative complication risks are in fact the same: vascular lesions (aorta, cavus vein and metameric vessels, with risk of medullary ischemia in case of ligature of the artery of Adamkiewicz, due to terminal bone-marrow vascularization). There also may be neurologic lesions of intra- or extracanal structures, and lesions of epidural vessels, pulmonary parenchyma or digestive organs. The risks of secondary diaphragm hernia or pleural effusion, however, are less than on classical approaches [20]. Minimally invasive approaches also involve a learning curve. This was clear in our own experience, with considerable blood loss (5L) in the first two procedures, due to metameric vessel wounds. Likewise, although our operating times have steadily diminished, they remain higher than those in the literature (Table 2). Finally, we found that although minimally invasive procedures reduced pain during the first year, quality of life was unaffected, with Oswestry scores similar to those for classical approaches. We use an enlarged work opening [26] with direct visual control of the operative site: a purely endoscopic technique would not allow installation of the cage. The benefit provided by surgery was as in the literature [27 30] (Table 2), with very satisfactory functional recovery (1-year VAS score < 1/10). Assessment criteria, however, vary between reports, especially as regards initial surgical kyphosis correction. For Payer, the criterion is postoperative regional kyphosis; for Knop and Lange, angular correction; and for Ulmar and ourselves, postoperative regional angulation. Although the patient s pretrauma spinal balance is unknown and RTA is no more than an attempt at assessing traumatic angulation, calculated from mean values that differ from the patient s, RTA still provides the best assessment of the deviation from physiological regional kyphosis [31]. In all series, secondary correction loss was of the order of 2. Only Payer reported functional results. The present is the only report comparing postoperative RTA and functional status between primary and secondary surgery: early intervention appeared preferable to revision for malunion, non-union or neurologic aggravation of vertebral body fracture. Finally, the ongoing development of cementoplasty holds out hope of an economic alternative in certain indications for anterior approaches. Conclusion Vertebral body replacement by anterior expandable cage provides satisfactory clinical and radiological results in traumatic thoracic and lumbar spine fracture. Enduring restoration of sagittal spinal curvature promotes functional recovery in trauma patients. Minimally invasive approaches optimize the procedure, but with a definite learning curve. Disclosure of interest The authors declare that they have no conflicts of interest concerning this article.

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